Revert "serial: of-serial: add PM suspend/resume support"

This reverts commit 2dea53bf.

Turns out to be broken :(

Cc: Jingchang Lu <jingchang.lu@freescale.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>